1. Field of the Invention
This invention relates to an improvement of a roll forming apparatus.
2. Description of the Prior Art
With respect to a roll forming apparatus to form a flat strip material into a channel form, such apparatus has been known as disclosed in Japanese Patent Application No. 128618/1981. In this conventional apparatus, the flat strip passes through a series of plural forming stations to have a channel shape. More particularly, the flat strip is disposed between a pair of forming rolls of each station, to thereby deform the cross sectional shape of the flat strip to be of a U-shape or V-shape in accordance with the shape of the outer surface of the forming rolls. In this apparatus, the forming rolls used at each station respectively drive the strip by means of a driving motor. Therefore the rotating speed of each of the forming rolls at each driven station must be a constant speed. When the rotating speed of the forming rolls of the respective station are different each other, such problems as, for example the deformation or twisting of the strip is caused at a respective station because different tensil stresses are applied to various portions of the strip.